========================
Clickjacking Protection
========================

.. module:: django.middleware.clickjacking
   :synopsis: Protects against Clickjacking

The clickjacking middleware and decorators provide easy-to-use protection
against `clickjacking`_.  This type of attack occurs when a malicious site
tricks a user into clicking on a concealed element of another site which they
have loaded in a hidden frame or iframe.

.. _clickjacking: http://en.wikipedia.org/wiki/Clickjacking

An example of clickjacking
==========================

Suppose an online store has a page where a logged in user can click "Buy Now" to
purchase an item. A user has chosen to stay logged into the store all the time
for convenience. An attacker site might create an "I Like Ponies" button on one
of their own pages, and load the store's page in a transparent iframe such that
the "Buy Now" button is invisibly overlaid on the "I Like Ponies" button. If the
user visits the attacker's site, clicking "I Like Ponies" will cause an
inadvertent click on the "Buy Now" button and an unknowing purchase of the item.

.. _clickjacking-prevention:

Preventing clickjacking
=======================

Modern browsers honor the `X-Frame-Options`_ HTTP header that indicates whether
or not a resource is allowed to load within a frame or iframe. If the response
contains the header with a value of ``SAMEORIGIN`` then the browser will only
load the resource in a frame if the request originated from the same site. If
the header is set to ``DENY`` then the browser will block the resource from
loading in a frame no matter which site made the request.

.. _X-Frame-Options: https://developer.mozilla.org/en/The_X-FRAME-OPTIONS_response_header

Django provides a few simple ways to include this header in responses from your
site:

1. A simple middleware that sets the header in all responses.

2. A set of view decorators that can be used to override the middleware or to
   only set the header for certain views.

The ``X-Frame-Options`` HTTP header will only be set by the middleware or view
decorators if it is not already present in the response.

How to use it
=============

Setting X-Frame-Options for all responses
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To set the same ``X-Frame-Options`` value for all responses in your site, put
``'django.middleware.clickjacking.XFrameOptionsMiddleware'`` to
:setting:`MIDDLEWARE_CLASSES`::

    MIDDLEWARE_CLASSES = (
        ...
        'django.middleware.clickjacking.XFrameOptionsMiddleware',
        ...
    )

This middleware is enabled in the settings file generated by
:djadmin:`startproject`.

By default, the middleware will set the ``X-Frame-Options`` header to
``SAMEORIGIN`` for every outgoing ``HttpResponse``. If you want ``DENY``
instead, set the :setting:`X_FRAME_OPTIONS` setting::

    X_FRAME_OPTIONS = 'DENY'

When using the middleware there may be some views where you do **not** want the
``X-Frame-Options`` header set. For those cases, you can use a view decorator
that tells the middleware not to set the header::

    from django.http import HttpResponse
    from django.views.decorators.clickjacking import xframe_options_exempt

    @xframe_options_exempt
    def ok_to_load_in_a_frame(request):
        return HttpResponse("This page is safe to load in a frame on any site.")


Setting X-Frame-Options per view
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To set the ``X-Frame-Options`` header on a per view basis, Django provides these
decorators::

    from django.http import HttpResponse
    from django.views.decorators.clickjacking import xframe_options_deny
    from django.views.decorators.clickjacking import xframe_options_sameorigin

    @xframe_options_deny
    def view_one(request):
        return HttpResponse("I won't display in any frame!")

    @xframe_options_sameorigin
    def view_two(request):
        return HttpResponse("Display in a frame if it's from the same origin as me.")

Note that you can use the decorators in conjunction with the middleware. Use of
a decorator overrides the middleware.

Limitations
===========

The ``X-Frame-Options`` header will only protect against clickjacking in a
modern browser. Older browsers will quietly ignore the header and need `other
clickjacking prevention techniques`_.

Browsers that support X-Frame-Options
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* Internet Explorer 8+
* Firefox 3.6.9+
* Opera 10.5+
* Safari 4+
* Chrome 4.1+

See also
~~~~~~~~

A `complete list`_ of browsers supporting ``X-Frame-Options``.

.. _complete list: https://developer.mozilla.org/en/The_X-FRAME-OPTIONS_response_header#Browser_compatibility
.. _other clickjacking prevention techniques: http://en.wikipedia.org/wiki/Clickjacking#Prevention